Induction heating



Feb, 17, 1942. N I w, WRIGHTQN 2,273,609

INDUCTION HEATING 2 Sheets-Sheet 1 INVENTOR. W/u/AMJ WR/am'o/v BY TRACY 6.522355% W 2 t ATTZJRNEY.

Feb. 17, 1942. w J WRIGHTQN ET AL 2,273,609

INDUCTION HEATING Filed Oct. 31, 1959 2 Sheets-Sheet 2 INV'ENTOR. I WILLIAM J' WRIGHTON y Tmcv CIJ'ARRETT EATTOIQNEY.

Patented l eh is; loss uurreo STATES PATENT oeelce This invention relete This application is e the earlier filed application having Serial No.

271,970, end being filed.

Due of the priricipal objects oi the invention is to provide an imoroved means and method of heating with err induction electric furnace whereby the distribution oi the heat in the means being heated by said :furiiacemay he positively controlled.

Another object is to provide improved means which is to he joined y the use oi an iiiclucti semhlya Another object is provide a novel apparatus,

clout lo. function for solder tending separate assooietecl memleersi Another object is urovide means which is simple end chi and method of forming cloted members a congeel and integral y under controlled an o work.

generated.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings and it will be apparent that 45 interval of time so as to avoid having the parts cool sumciently to cause the solder used in uniting the parts or lamination to congeel prior to being subjected to pressure and also includes the danger of having the parts move out of desired The invention, 50 aligned relation with each other.

With such prior art procedure, particularly when gas furnaces and the like were used, heat temperatures and distribution of the heat could not be accurately controlled. There was danger of the work'becoming overheated with the result many changes may he s to induction electric furnaces and has particular reference to improved meeus and method of heating through the use oi such iurriaces.

Zl electric tor sociated means for substantially uniformly distributing heat throughout salt; laminated esa controlled s suhiectlug them to inductive heat to cause of pressure.

Another object to provide a novel apparatus for heating work while holding worlr under e given pressure whereby the host will be sub-- stautially entirely generated end will be sub stahtia-lly uniformly distributed throughout the INDUCTION HEATING Applieatioh October 31, i939, Serial No. 302,210

2 (Claims. (cl. 219-13) May 5, 19%.

heat gtlllftlllifiti through heeting unit.

For ease or": description pre u will he described for use in glol of laminated members or lay soldering said layers togetheiz stood, however, that the he tiiie appa atus em assembly of asso 2 5 hoclying the invention will oe used o'der medium therehedifferent 13111100565,

the solder to melt or "suite some while held made in; the details of is to under In joining laminated so." has been usual to hold: the by separate clamp means who flow between the members upon cooling to 39 110111 the parts in P for sll-bseqlll'lll Fig. I is a plan view of o composite limited assembly which is to he hosted by the heating apparatus involving the invention and showing the means for controlling the distribution of heat to said assembly;

Fig, H is e longitudinal section view taken as on line lI--ll of Fig. I and looking in the directime indicated by the arrows;

Fig. III is a front elevation of the heating lo apparatus embodying the invention showing portions thereof in cross section;

Fig. W is a side elevation of said apparatus;

Fig. V is o plan view of the heating coil end.

lower supporting jaw of the pressure apps-rams and method of hes-tine; a lemihe-Jted essemhlv lll with e. diegrammatical illustration of the transformer and current control of the meeting unitof said apparatus; and

Fig, V1 is a side elevation. of the soil the With the prior tor {several eg The assembly held by such clamp means placed in furnace heated. by gas or the like. These prior art furnaces were of such nature the heating of the lamination was by tion and conduction and required a relatively long interval of time to produce a substantially uniform distribution of heat.

arrangement of heat the clamps or other supporting means for the assembly were heces-. ment for controlling the temperature of heat 40 arilv ea e te suc hea e a nate assembly was removed irom the furnace end released under a separate press. This shift of the laminated assembly from the iurrlace to the press had to be carried out in a relatively short that solder was burned or, in instances when a precious metal layer was being joined with a base layer, the metal would become too soft or molten. With such prior art devices, uniform pressure could not be applied while heating. All of these difficulties endangered the making of uniform solderings and in many instances during subsequent working of the joined laminations, the solder bond would not resist such workings and allowed portions of the laminations to become disunited. This was mostly due to the fact that the heat could not be substantially uniformly distributed through the parts being joined and even pressure could not be applied to said parts during said heating.

The essence of the present invention, therefore, is to provide an arrangement whereby pressure may be applied directly to the work during said heating, the heat definitely controlled and substantially equally distributed throughout the laminations or work during the heating thereof.

Referring more particularly to the drawings, wherein like characters of reference designate like parts throughout the several views the work or means which is to be heated as shown in Figs. I and II comprises a layer I of base metal and a layer 2 of precious metal such as gold and a layer 3 of solder therebetween. The layer 3 may be of hard solder or of any desirable joining material. In forming this assembly the surfaces to be joined by the solder are cleaned and properly fiuxed. The flux may be of boric acid or other known suitable fluxes, The assembly thus formed is provided on the opposed sides thereof with a relatively thin layer of paper 4. Directly superimposed on said layers 4 there is provided layers 5 of heat resisting material such as asbestos or the like and are of a controlled given thickness. There is superimposed on these heat resisting layers 5 plates 6 of copper or the like of controlled given thicknesses and of controlled conbe joined. The plates 6 may be provided with a relatively thin inner facing I of stainless steel which lies between said plate 6 and heat'resisting plates 5. To insure proper bonding at the edges of the assembly the said edges may be given a coat of similar flux as that used on the surfaces. This is applied to the edges after the parts or layers to be joined are in assembled relation with each other.

The assembly formed as specified above is then placed in the heating and compressing device embodying the invention such as illustrated in Figs. III to VI inclusive. This heating device comprises a pair of jaws B and 9 formed of a plurality of. superimposed transformer iron laminations, that is, a plurality of thin metal plates held in superimposed relation with each other by connecting bolts or other means I0. These relatively thin metal plates or transformer iron laminations are so joined with each other as to form relatively flat and, parallel faces II and I2 which are adapted to engage the work l3 to be. heated. which in this particular instance is described as superimposed laminations having a layer of solder therebetwcen such as shown in Figs. I and II.

The jaw 8 is supported by insulation material l4 connected with a bracket by brass bolts or the like I 6. The bracket I5 is supported by a plurality of uprights ll carried by a base 18. The jaw 9 is similarly supported by a bracket l9 having bearing members which may be moved longitudinally of the upright ii. The jaw 9 has insulation material 2| secured thereto by brass bolts or the like 22 which is engaged by a plunger 23 of a hydraulic pump 24. The hydraulic pump 24 is supported on the base I8 and may be operated by a pump lever 25 or by an automatic means as desired. The said pump has a suitable indicator 25 associated therewith indicating the amount of pressure applied to the jaw 9.

It is to be noted that the assembly of work I3 is placed upon the lower jaw 9 and that pressure is applied thereto by the hydraulic compression pump 24 by moving the jaw upwardly into engagement with the upper jaw 8. Due to the fact that the faces H and i2 of the jaws are substantially parallel, substantially uniform pressure will be applied throughout. The total pressure which has been found from practice to be desirable is from 2000 to 3000 pounds. This pressure is suitable for use in hard soldering a precious metal layer to a base metal such as copper, nickel or silver.

An induction coil 21 such as shown in Fig. VI is supported so as to surround the laminations of the jaws 8 and 9 in the assembly I 3. This induction coil is preferably formed of tubular material 28 bent so as to produce a plurality of superimposed coils of a rectangular shape of a size which will surround the jaw members 8 and 9 and the work or assembly i3 carried thereby. The coils contain a cool liquid such as water which is flowed inwardly thereof through the inlets 29. A suitable outlet 30 is provided whereby a continuous flow of the water or cooling liquid takes place. The cooling water or liquid is for the purpose of keeping the coil member 21 cool so that the resistance in the coil will be less and the resistance loss less. The superimposed coils 28 are held in spaced relation with each other by a plurality of spaced members 3| of heat resisting material such as asbestos or the like and by tie members 32 of insulation material such as wood or the like held in position by connecting bolts 33. The parts of the coil for the above are thereby joined into an integral unit which is supported by the spaced plates 34 and 35 of heat resisting material such as asbestos fabricated into a stiff plate like member commercially known as Transite board.

The coil is surrounded by walls 36 of similar material. These walls have a plurality of slotted openings therein. The plates -34 and 35 are connected adjacent the opposing ends thereof to sleeve members 31 operably mounted on the upright IT. The plate 34 is connected to a steel cable or the like 33 which extends over pulleys 39 carried by the upper bracket l5 as illustrated in Figs. III and IV. The cable 38 is attached at its opposite end 40 to the lower bracket l3. When the bracket 19 is lowered the cable 38 is adapted to draw the plates 34 and 35 and the coil 21 mounted therebetween upwardly so as to expose the upper face 12 of the jaw 9. When the jaw 9 is moved in the opposite direction or up wardly the coil and associated support will simultaneously move in a downward direction. A suitable stop collar 52 mounted on the upright H is adapted to limit the downward movement of the coil 21 and associated support therefor;

The arrangement is such that when the laws 8 and 0 engage the assembly I3 the said assembly will be located substantially centrally of the coil 21.

The coil members 21 are connected through suitable lead wires 4| and 42 to a transformer 43 capable of varying voltages and amperes. The lead wire 4! is connected to one end of the secondary coil Moi the transformer. The lead wired? is provided with aline switch 45 of any desirable type. The said lead wire 42 is connected through the switch G5 to a plurality of switch members to which may be selectively opened or closed. That is, such members d6 are connected, as by'the lead wire ll, to different taps on the transformer coil i l so that different voltages may be obtained. The primary coil 48 of the transformer is connected by the lead wires 59 to any suitable source of A. C. electrical energy. It is to be noted that the plane of the transformer plates forming the jaws 8 and 9 is at substantially right angles to the longitudinal plane of the assembly is and the inductance coil all. The purpose or this arrangement is to concentrate the high amperage circulating current in the assembly The circulating current generates heat energy in the assembly The flow oi the current passing through th assembly of worlr generates the heat and the extent of this current is controlled by the switch member tlhange oi the distance between the jaws d and ti necessitates change in the voltage used and is controlled by closing-the proper switch of the transiormer The switch 55 may be of the con'inierciaily known time switch type as desired whereby the l ngth of exposure of thevassembly is to the inductance coil may be controlled. The assembly comprising the jaws 8' and ii and inductance coil it, is of the lower frequency type, approximately 60 cycles, so that heat is generated in a relatively short time interval, This type transformer and assembly may be designed for any of the commercial power frequencies. Commercial power frequencies are used because of great depth of penetration of, the current. With this type of heating unit maximum useful heat is generated only in the assembly .The purpose of using insulation material ill and all, and the use of brass bolts for joining laminations S and 9 to insulating material, is to diminish and isolate the magnetic field.

The copper plates ti illustrated in Figs. 1 and I; are for the purpose of controlling the distribut tion of the current in the assembly it. By changing the shape of the plates a difierent distribution of the current is obtained so that the shape or such plates is factor controlling th substantially uniform distribution of heat throughout the assembly. It has been found that the operation of the field of inductance can be definitely controlled by the shape of the plates 6.

It is to be noted that in this particular instance the plates 6 are formed with a central portion 5t substantially the same widthas the width of the laminations i and 2. The ends 5i of said plates are enlarged so as to protrude considerably beyond the opposed ends of said assembly. The purpose of forming the central portion iii! of the plates *5 with a width less than the width of the ends is to avoid overheating the assembled laminaticns l, and 3 throughout the central area thereof. It has been found from pastpractice that should the plates 6 be formed rectangular in shape and of substantially the same shape as the layers to be joined, an excessive amount of heat will be generated in the center or heat of a lower intensity will be generated at the ends. In order to balance the d stribution of heat, the plates are reduced in width through the center area thereof. By controlling the width of the center area in proportion to the width of the end areas 5i a substantially uniform amount of heat may be generated throughout the entire assembly. The shape of plates 6, therefore, depends on the shape of the laminations which are to be united or which are to be joined. In instances when the work is of the nature set forth herein. that is, a laminated assembly having a layer of hard solder therebetween. heat is generated to a temperature which is above the melting point of the solder. immediately upon the detection of the flow of the solder the electrical current is shut off, either automatically or manually. The assembly is then allowed to cool while held under pressure by the hydraulic pump This is also true of soft solder. it is also to be noted that during the soldering operation pressure is maintained substantially constant.

in forming the assembly ill the relatively thin sheets or paper l are positioned between the layers and the immediate surface of the laminations i and 2 which are to be joined for the purpose of preventing the asbestos layers from adhering to the outer surfaces or the assembly after the solderin operations have been completed. The stainless steel facings l on the copper plates are for the purpose or" preventing any solder which may flow outwardly from adhering to the plates 6.

Although the device embodying the invention has been. shown and described as being used for solder uniting laminated assemblies, it is to be understood that said heating apparatus may be put to any desirable use such as for heating dies for hardening purposes, for use in brazing operations, for melting metals, or for any desirable heat treatment.

Although the plurality of relatively thin transformer iron la'rninations are specified as being used in forming the jaw members and it is to be noted that these laminations constitute part oi the induction furnace and function cooperatively with the coil 2? in generating the heat desired.

From the foregoing description it will be seen that simple, efilcient and economical means and methods have been provided for accomplishment of all oi the objects and advantages of the invention, particularly that of generating heat through induction and controlling the distribution or" said heat.

l-laving described our invention, we claim:

l. The process oi substantially uniformly solder uniting an assembly of superposed metallic plates comprising placing asheet of bonding material between the adjacent surfaces of a layer of precious metal and a layer of. non-precious metal, forming heater strips of heat conducting metal each to a controlled shape and size with respect to the shape and size of the metallic strips to be solder united so that the said heater strips will have a central area of a width no greater than the greatest width of the metallic layers to be solder united and each having end areas greater than the adjacent end areas of said layers with the said end portions of said strips protruding outwardly of the sides and ends of the adjacent portions of said layers, said central area and end areas of said heater strips being so proportioned according to the respective adjacent areas of the strips as to cause substantially uniform heat distribution throughout the total area of said strips, a. further step of subiecting the superposed metallic members and the heater strips to uniform compression while inductively heating the superposed member and the heater strips until the bonding metallic end that the superposed metallic members to be soldered together are thoroughly compressed while the bonding material is in a state of flux and holding the superposed metallic members under compression until after the bonding material has set.

2. The process of substantially uniformly sol der uniting an assembly of superposed metallic plates comprising placing a sheet of bonding material between the adjacent surfaces of a layer of precious metal and a layer of non-precious metal, forming heater strips of heat conducting metal each to a controlled shape and size with respect to the shape and size of the metallic strips to be solder united so that the said heater strips will have a central area of a width no greater than the greatest width of the metallic layers to be solder united and each having end areas greater than the adjacent end areas of layers will be in proper relation with each other v to bring about said substantially uniform heat distribution, subjecting the assembly thu formed to substantially uniform compression throughout the areas of the metallic layers to be solder united and subjecting said assembly to inductive heating while maintaining compression on said metallic strips to be solder united.

WILLIAM J. WRIGHTON. TRACY C. JARRE'IT. 

